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Thursday, January 8, 2015

Rachel Maddow recently interviewed
one Mr. Frank Schaeffer, a self-proclaimed
Christian moderate, who proceeded to rail against the ignorance and stupidity
of Christian fundamentalists. While I found myself generally agreeing with this
gentleman's statements, I found the diatribe to be rather odd. To be specific,
it wasn't that what was said was odd, but rather that it was odd to be coming
from a gentleman who admittedly holds irrational beliefs himself.

Here's Mr. Schaeffer's argument, as best as I can tell.
Christian fundamentalists (CFs) hold obviously silly beliefs, such as that the
Earth is 6000 years old, that dinosaurs roamed the Earth with humans, and that
there was a man Noah that managed to pack two of every creature on the face of
the Earth into an ark. Mr. Schaeffer therefore concludes (correctly) that CFs
are just plain ignorant, and almost explicitly asserts that it is willful
ignorance. As such, the CFs are just plain nuts. Cuckoo.

Here's the problem: Indeed, the CFs hold a whole host of
irrational beliefs. Let's denote the entire set of irrational beliefs held by
CFs to be X. Now, the more moderate Christians (MCs), Mr. Schaeffer being one,
also obviously hold irrational beliefs, such as the reanimation of the dead and
other assorted miracles. Lets call this set of irrational beliefs Y. It's
probably safe to say that the number of elements in X are greater than Y.
Furthermore, it is definitely safe to say that the intersection of X and Y is
not an empty set. So, Mr. Schaeffer's argument against CFs really boils down to
the following: CFs are nuts, because there are elements in the set X that are
not part of his irrational belief system Y, and furthermore, the CFs hold a
greater number of irrational beliefs than he. Or more simply, "If you
think I'm cuckoo, have a look at that guy!"

Now, to someone that holds as close to zero irrational beliefs
as humanly possible (or strives to anyway), this is absurd. As far as I'm
concerned, both the CFs and the MCs are cuckoo. This is not a numbers game
where the level of insanity is determined by simply adding up the total number
of elements in sets of irrational beliefs. "You believe in pink and blue
unicorns, whereas I only believe in the pink. You sir, therefore, are nuts."
is not exactly a sound logical argument.

In fact, Mr. Schaeffer misses the mark completely. The danger is
that anyone with irrational beliefs can act upon them; that is, their actions
may be guided or justified by such irrational beliefs. It is not the number of
irrational beliefs that matter. The holder of one single irrational belief can
be just as dangerous, or even more dangerous, than those who hold many, if such
a person acts upon that belief. You sadly see this behavior much too
frequently, for example, from parents who murder their children after claiming
that they or their children were possessed by the devil (or some similar
irrational rationalization). Don't even get me started about the Pope, who
believes in some ridiculous soul-sperm-ovum-person-thingy that has killed
numerous thousands through lack of condom use. It only takes one irrational
belief.

I contend that CFs are dangerous, not because X > Y, or that
certain elements of X are more irrational than Y (as if something irrational
could be more irrational than something else!). No, it's that CFs are
determined to impose their irrational belief system X upon those who believe Y,
and especially upon those, like me, that hold an empty set of irrational
beliefs. While MCs may be relatively benign now, there is a latent potential
for danger. All irrational beliefs are potentially dangerous. One irrational
nut calling another irrational nut insane is certainly accurate, but it is not
self consistent. Both are nuts.

So, to Mr. Schaeffer I say, "You're right, the
fundamentalists are cuckoo. And so are you."

Wednesday, May 21, 2014

Daniel Dennett earlier this afternoon delivered at the Atheist
Alliance Conference in Montreal a talk entitled, "What Should Replace
Religion?". It's a rather presumptuous question, which Dennett
admitted at the outset. I've never seen him speak in person, but his
roughly one hour presentation was in line with those I've viewed on youtube:
clear, concise, entertaining, and thought provoking. Unlike his
other presentations, however, his thesis was wrong. Clearly wrong.

The premise of Dennett's thesis was not really "What should replace
religion?", but what positive elements or products of religion should we
consider retaining? He provided a laundry list of possibilities that
included hope, love, music, art, and community. There were quite a few
more items in the list, but I can't remember them all and it's actually
irrelevant. It's irrelevant, because everything on his list is not the
sole domain of religion any more than morals are owned by religion.
Would music disappear in the abscence of religion? Love? Hope?
Community? No. Isn't this obvious?

To be sure, religion has had influence on many things. Music can be
inspired by religion or religious experience. Dennett gave the example of
the Bach cantatas that are performed at a local church just outside Boston.
Bach was a musical genius--one of the greatest composers in the
history of the modern world. Would he have failed to compose music
without religion? I think not. While I'm orders of magnitude below
the capabilities and talent of Bach, I compose, arrange, and perform music
without any religion at all. I suspect that Bach's inate music ability
would have found an outlet in a secular society if such a thing existed in
early 17th century. And I would suggest his musical output would be no
less spectacular. Turning to modern times, Dennett provided a further
musical example: gospel music. Clearly the lyrics of gospel music are
religious and the performance of gospel has roots in the church. But,
would have gospel music failed to emerge under a secular history? Maybe.
Maybe not. I am certain that some sort of music, perhaps a new
genre that we will now never know precisely because of
religion, would have emerged from the experience and struggles of blacks in the
south. Maybe we'd have secular gospel music, not unlike the new gospel
music that got Dan waving his arms in the air, as well as a few others in the
crowd. Music is not owned by religion. Therefore, there is
no need to consider whether it is a quality that we should consider retaining
from religion.

Daniel
Dennett gets "religious" listening to atheist gospel music:

gospel-style
music with secular and atheist lyrics.

The same argument applies to love, hope and everything else on the list.
Can atheists love? Sure. So, why is that a quality that
should be retained from religion. It's not a religious quality at all.
I'm rather shocked--disappointed, actually--that Dennett would make
such an obvious error in reasoning. There is nothing of value that
religion provides uniquely. Nothing. It provides no knowledge or
insight into the understanding of the universe, and it has no claim to morals,
emotions, music, art or any of the other valuable qualities of the human
experience. I would suggest that rather than promoting the items on
Dennett's list, religion often suppress and destroys many of the positive
aspects of life that we cherish. Hope and religion: hope that you
don't burn in hell? Love: unless of course your gay.
Community? Sure, as long as you have the correct religion otherwise
you burn in hell.

I'm sure a youtube recording of the presentation will be made available soon.
I'll post an update with a link if and when that happens so that you can
listen and decide for yourselves.

Wednesday, April 10, 2013

In “The Moral Landscape”, Sam Harris argues that morality
can be determined by considering the impact of actions on social well being. The impact is quantifiable through the
relative comparison of possible social states arising from different actions. A moral action is one that produces the
greatest relative maximum in the topology of possible states of societal well being. Let us take this definition of morality as an
axiom. For the purposes of this piece,
it matters only that Sam Harris believes it to be true not that it is true.

Now also consider Sam Harris’ position on guns. He argues vociferously for the right to own
guns. Lots of them. Of many kinds.
For example, in his “The Riddle of the Gun” he writes:

“Wouldn’t any decent person wish for a world without guns? In
my view, only someone who doesn’t understand violence could wish for such a
world. A world without guns is one in which the most aggressive men can do more
or less anything they want. It is a world in which a man with a knife can rape
and murder a woman in the presence of a dozen witnesses, and none will find the
courage to intervene.”

This is, of course, a strawman argument. Few are calling for a world without guns,
although it is reasonable to ask whether such a world would be in a state of
greater well being than a world where guns are ubiquitous. Does it really follow that in a world without
guns that a man with a knife can rape and murder? Are law abiding citizens really helpless in a
world without guns? Do we see women
being raped and murdered across Western Europe where guns are generally far
less common than in the U.S.? Is crime
rampant in the UK where not even the police carry firearms (except for Ireland)? And, couldn't non-lethal methods be used? How about tasers or pepper spray? Are guns the only defense we have against violence? It's a strawman and a false dichotomy.

The reality is, reasonable people are calling for greatly
limiting access to firearms or removing certain types of firearms from
society. Is the resulting scenario a state where
well being would be increased? Suppose
only law enforcement carried firearms so as to protect law abiding citizenry
from violence. Would this result in a
state of higher well being than we have now?
Conversely, would well being be increased by increasing the number of
guns and allowing nearly everyone to carry multiple firearms at all times?

Measuring well being is subjective, so reasonable people
might disagree over whether one possible outcome is better than another. However, it seems that in the spectrum of
possible states of well being, a society in which there were no guns, or at the
very least, a society where only law enforcement carried firearms would be
better off than a society where guns flow like water. And a society with non-lethal weaponry might be yet an even higher state of well being.

Sam Harris’ moral landscape position seems incompatible with
his stance on gun control. He has
provided all sorts of arguments to support his position on guns, but interestingly,
he has not yet, as far as I know, argued his position in terms of the moral
landscape. If morality can indeed be
quantified by testing actions against their effect on well being, then Harris’
best argument for guns would be to show that a society armed to the teeth is
better off than a society without firearms.
Good luck with that one, Sam. I suspect that in the end, you'll have to choose either guns, or the philosophy of the moral landscape, or reject both. But you can't have both guns and the philosophy of the moral landscape.

Thursday, August 9, 2012

It's not uncommon that I hear incorrect explanations for the origin or behavior of various atmospheric phenomena. This post was inspired by a recent event where an individual insisted that "extreme pressure variations" are needed to produce a hurricane. Below, I describe the actual mechanisms that produce a hurricane. It turns out the same physics may also be responsible for producing some Mars dust storms.

Consider first a motionless atmosphere with no horizontal pressure variations at all. That is to say, there is no wind and if you were to look at a weather map you would see no high or low pressures. It is from this state that hurricanes (also known as tropical cyclones) develop. Immediately, you can see that if this is indeed the initial scenario, then the assertion that "extreme pressure variations" are necessary is exactly wrong.

In reality, there is no such idealized state in the atmosphere. There is always some amount of pressure variation and therefore some amount of wind. The process I will describe below works just as well as long as these winds and pressure variations are small.

From this rather boring initial state, heat a chunk of air near the surface from the sun. It becomes buoyant like a hot air balloon, and rises. In the tropics, it is not unusual that such rising motion will develop into individual thunderstorms. Inside a thunderstorm, water vapor condenses, which releases heat. This heating causes the air to expand. (Slightly technical here: this is an adiabatic expansion, meaning that no net energy is being added; even though there is heating due to condensation, it is internal heating and represents no external energy input). This expansion has the effect of causing a weak low pressure to develop near the surface and weak high pressure to develop aloft. Once there is a low pressure at the surface, horizontal winds develop and begin to flow toward the storm.

If the thunderstorm is over water, the wind now flowing toward the storm interacts with the underlying ocean. The interaction is actually quite complex, but I'll distill the essential and relevant parts here. If the ocean is warmer than the air, the air will be heated through turbulent eddies transporting the heat of the ocean upward. The strength of the turbulent eddies and therefore the efficiency of the exchange is related to the wind speed and the difference in temperature between the atmosphere and the ocean surface. If the wind is strong (all other things being equal) the exchange will be strong. If the temperature difference is strong (all other things being equal) the exchange will be strong.

In the case we have so far, the winds are rather weak, so the exchange is rather weak. Nonetheless, energy is being added to the atmosphere and carried toward our thunderstorm. (Actually, it is entropy that is being transported, but it's not important at this level of discussion, and I digress...) As the air flows toward the weak low pressure, it expands. Normally, this expansion would cause cooling. However, the warm ocean underneath keeps the temperature of the air nearly constant as it expands. In other words, the heat the air receives from the ocean nearly balances the cooling due to expansion. This is called an isothermal (same temperature) expansion process.

Once at the storm, the air rises, condenses, and heats the atmosphere. This strengthens the low pressure at the surface. In turn, this increases the wind speed flowing toward the storm. And this in turn increases the heat exchange between the atmosphere and the ocean (recall that the magnitude of the exchange is related to the wind speed).

It should be clear that what we have is a feedback process. It's a process that reinforces itself. As more energy is picked up by the air flowing towards the storm, the more heating is produced in the storm, the lower the pressure drops, and the stronger the winds get. If you look at the entire system of air flowing toward the storm, air rising in the storm, air flowing out of the storm aloft, and then sinking away from the storm, you have a complete cycle. Approximately 30 years ago the thermodynamics of this system was recognized in two landmark papers (you can get them here and here). It turns out to be a sort of Carnot engine. The process was called "Wind-Induced Sensible Heat Exchange", because it coupled the wind to the exchange of heat energy with the ocean. While the fine details of this mechanism are still being debated in the literature, the overall process is now well established. In essence, the engine extracts heat from a source, in this case the ocean and turns it into mechanical work (in this case increasing wind speed).

For simplicity sake, I've left out a lot of details, but these are not relevant to the big picture here. There is at least one detail that is relevant: The Earth rotates. This means that as the air moves, it will experience an apparent deflection. If the movement is over a sufficiently long time, this will result in the air beginning to rotate around the low pressure rather than flowing toward it. If nothing else were to happen, there would be no air flowing to the storm, just going around it. That would be the end of the storm. But, there is friction. Friction keeps some component of the motion always flowing toward the low pressure. Thus, the feedback process may continue. Furthermore, because friction is also a function of wind speed, the strong the winds, the stronger the friction, which dictates how much energy can flow to the storm.

The above process is the basic concept of how hurricanes develop. No "extreme pressure variations" are needed. The storm can develop from a completely motionless atmosphere with no pressure variation at all. It actually depends on the lack of an initial pressure variation.

Why don't all storms develop into hurricanes? There's lots of things that can mess up the feedback process. One is that the system moves over land. Then there is no heat exchange with the ocean. Another is that the initial storm can be too close to the equator. The deflection of winds at the equator is zero, so no rotation can develop. If the storm moves to higher latitudes, the ocean can become too cold and this limits the energy that can be provided. Another major hindrance to storm formation is the presence of strong wind shear. Wind shear is a change of wind speed or direction with height.

Here's the thing about wind shear: Wind shear results when there are strong pressure variations. For example, the jet stream is a result of strong large scale pressure differences. Hurricanes and jet streams just don't get along. The strong winds that result from the strong pressure differences literally rips the hurricane apart by shearing the top of it off.

Not only do hurricanes not form because of extreme pressure variations, they are prohibited by extreme pressure variations, because such variations produce wind shear.

Obviously, once a hurricane forms, it has strong pressure variations related to the storm itself. This is not what causes the storm however. The strong pressure variations are a result of the storm, not the other way around. The hurricane is produced by the Wind-induced Sensible Heat Exchange--a process that transfers heat from the ocean to the atmosphere. The process depends upon having a relatively flat pressure field for it to start and proceed. Again, if extreme pressure variations are present the associated wind shear will disrupt the entire process.

I mentioned early on that a similar process may occur in some Mars dust storms. I published a paper about this a couple of years ago (here). Dust essentially provides the heating on Mars. As air flows toward the storm, dust is lifted, and that dust is radiatively heated by the sun. Winds increase in the disturbance and this causes more dust to be lifted. Thus, I named the process Wind-Enhanced Interaction of Radiation and Dust (WEIRD) in recognition of the WISHE analog to hurricanes.

Wednesday, September 1, 2010

I was recently presented with the statement that “life is the only force that counters entropy”. This can be taken to mean one of two things. The first is that life results in a net decrease in entropy. The second is that while life may result in a net increase in entropy, entropy of the life form itself is reduced and life is the only such system that can do this. The first argument is nonsense, as it violates the 2nd Law of Thermodynamics. The second statement is just plain false; there’s nothing thermodynamically unique about life. Let’s look at both situations to understand why.

The first order of business is to define entropy. There are lots of valid definitions and all valid definitions can be shown to be equivalent. One definition of entropy is the amount of energy that cannot be used to do work. Doing work requires energy. For example, if you want to move something, you need to expend energy. Except for theoretical systems, whenever energy is expended by a system, some of the energy is wasted—not all the energy can be used to do work. For example, when you move an object, you expend energy to flex your muscles, and this is translated into kinetic energy (energy of motion). As your muscles flex, heat is created. This heat is sent into the environment and is not used to move the object. Thus, entropy is increased in an amount related to the wasted energy.

The inefficiency of systems that do work is at the crux of the 2nd Law of Thermodynamics. In a theoretically perfect system, all the energy would go to do work and no heat would be generated. a perfect system can at best use all energy to do work (resulting in no net decrease in entropy). An imperfect system (e.g., a real world system) will have an inefficiency so that some energy is wasted. The wasted energy produces a net increase in entropy. No system can do work to produce more energy than is needed to do the work. This would be a perpetual motion machine and it would generate a net decrease in entropy.

We can now investigate whether life counters entropy. The answer is no, at least not in the global, net sense. Life can do work (e.g., grow, reproduce, move, etc.), but all these processes involve an inefficient expenditure of energy. Life increases entropy. Period.

Now let’s look at the second possible meaning of “life is the only force that counters entropy.” To do this, let’s consider a different, but equivalent measure of entropy. Entropy is also a measure of organization (or disorganization). A system that moves toward more order has a decrease in entropy. The existence of such a system may seem impossible given the discussion above, but it is not. A system can have a decrease in entropy at the expense of its surroundings. The surroundings will suffer a larger increase in entropy than the decrease in the system, resulting in an overall increase in total entropy. There are a multitude of examples of systems in which entropy is decreased.

Life is indeed one such example. Cells and organisms are assembled from a more disorderly system of atoms and molecules. Life takes in nutrients and assembles these into orderly functioning life systems. So, in this sense, one could say that life counters entropy. This of course ignores that life, on the whole, actually increases entropy when life plus its environment is considered. The outstanding question is whether life is the ONLY system to do so. The answer is clearly and resoundingly, “no”.

Well known examples of systems that have a reduction in entropy are air conditioners and refrigerators, crystal formation, and planet formation. The true list of such systems is possibly infinite. Air conditioners produce cold air from hot air. The cold air is slightly more ordered than the hot air. Entropy decreases. But this is only true if the waste heat is neglected. Anyone that has spent even a small amount of time around an air conditioner knows that in order to produce cold air, hot air—much hotter than originally ingested—must be
ejected. So, in net, entropy increases. Entropy is lower in the cold air, but it is higher in the hot air, and the net effect is an overall increase in entropy. Crystals are very orderly. This order represents a reduction of entropy compared to the original unorganized, uncrystalized molecules. But, as in the previous example, the environment suffers a larger increase in entropy in order to allow for crystallization. Cyrstalization generates waste heat and, therefore, an increase in entropy. The net change in entropy is positive. Solar Systems form from a collection of gases and dust. These spiral in and accrete into larger bodies, eventually becoming planets—a more orderly arrangement. But, this process generates heat, and the entropy generated from solar system formation exceeds the reduction in entropy associated with greater organization.

So, there you have it. The first interpretation is wrong and the second interpretation is wrong. Life does not counter entropy, at least in the global sense. Life increases entropy. The second interpretation is wrong even if life is viewed in isolation from its surroundings. In such a situation, life produces a reduction in entropy in the isolated life system, but there is nothing unique about this process. Lots of systems, in absence of their environment, constitute a reduction in entropy. Life is not the “only” system to do so.

Making a statement such as “life is the only force to counter entropy” is at best misleading, because it implies that life has the overall effect of decreasing entropy. It can’t do this, because of the 2nd Law of Thermodynamics. If the proponent of such a statement tries to hide behind the canard of only talking about the system in isolation, they will find themselves once again in the wrong corner, because life is not in any way unique in this regard. In short, there’s nothing thermodynamically special or unique about life.

Sunday, January 3, 2010

The Death of Planets. No, not the planets themselves. The idea or concept of what we have recently called planets is doomed, with the demotion of Pluto to a dwarf planet being the most recent step in a process that began with Copernicus. Then end game will be the realization that the concept of a planet as a meaningful astronomical class of objects is antiquated and archaic. The concept of planet is no longer compatible with what we know about the Universe. The bickering by a minority of astronomers about the definition of a planet, and which has achieved tremendous exposure in the public arena, is as pointless as the flat Earthers arguing about whether the flat Earth is rectangular or circular.

Since humans first looked up at the night sky, they noted that there were some objects, often brighter than the rest that did not follow the other objects in their regular movement across the sky. The ancient Greeks labeled these objects as “The Wanderers”, or as we know them, planets. Thousands of years ago, the segregation of these special objects from the rest of the celestial chaff made sense; they were clearly different than all the lights in the night sky, and there was no mistaking what was a planet and what was a star.

The path of Mars against the fixed stars as viewed from Earth. Click on Image to see animated version. (Image Source: Unknown)

Then came Nicolaus Copernicus(19 February 1473 – 24 May 1543) and Galilei Galileo (15 February 1564 – 8 January 1642). In less than a century, the crystalline spheres upon which the stars rode and the Ptolemic epicycles that described the motion of the planets, came crashing down. The wanderers were in orbit about the Sun, not the Earth, and they were not just points of light, but other worlds. Some like Jupiter, had moons, just like Earth. Luna, the Earth’s moon, had mountains and craters. And there was more, much more. The skies were crowded with stars that could not be seen with the naked eye, but which revealed themselves through magnification (this includes nebula and galaxies which could not be easily distinguished from individual stars back then). The origin of the “milkiness” of the Milky Way became obvious—it was composed of stars, packed so closely together in such great density that they appeared as a hazy cloud.

Until 1781, the number of known planets remained at six, all of which could be observed by the naked eye without the aid of a telescope (Mercury, Venus, Earth, Mars, Jupiter, and Saturn). Sir William Herschel discovered Uranus in 1781. Neptune was discovered by a Ph.D. student, Johann Galle in 1846, based on predictions provided by Urbain Le Verrier, which explained the small orbital perturbations of Uranus. The search for a ninth planet (at the time needed to explain additional perturbations in the orbits of Neptune and Uranus, but no longer needed now that the masses of the previous eight planets are better constrained) was ended in 1930 with the discovery of Pluto by Claude Tombaugh. Pluto was a bit of an odd planet. It was very small, but more importantly, it orbited in a plane about the Sun that was significantly different than all the other planets. Neither Uranus, Neptune nor Pluto can be seen without a telescope.

The orbits of the classical planets about the Sun. All but pluto orbit in nearly the same ecliptic plane. (Image Source: Unknown)

Oddly enough, what we now call an asteroid named Ceres, was discovered in 1801 by Giuseppi Piazzi. Like the other known planets at the time, it was a wanderer, in orbit about the Sun between Mars and Jupiter. By all accounts Ceres was a planet, and although not known at the time, it was spheroidal like a planet. Indeed, it was considered a planet at the time of its discovery. Within a year or two, the inner Solar System began to get a lot more crowded. Pallas, Juno, and Vesta were discovered, also in orbit about the Sun between Mars and Jupiter. It was not long before dozens and dozens of these objects were found. By the turn of the century, there were hundreds.

For no other reason than their location between Mars and Jupiter, these objects which had all the same orbital properties of the classical planets, were put into a new class of objects, called asteroids, as suggested by Sir Herschel (the discoverer of Uranus). However, for many years, the terms planets and asteroids were used interchangeably in the scientific literature. By the time thousands of the objects had been discovered, the need to distinguish within the literature the classical planets from these minor planets led to the acceptance of the term asteroid (as well as minor planet), which has remained to this day. Importantly, at the time, the distinction between asteroids and planets was merely one of convenience.

Asteroid and former planet Ceres, as viewed through the Hubble Space Telescope by my friend and colleague J. Parker at Southwest Research Institute. Ceres is massive enough that its shape is spheroidal. (Image credit: NASA)

For more than a hundred years after the discovery of the first asteroid, Ceres, the known objects in the Solar System consisted of the Sun, the classical planets and their moons, the asteroids, and the occasional comet. Then, suddenly, the population of the Solar System once again exploded.

Dave Jewitt and his former graduate student Jan Luu found the first Kuiper Belt Object (KBO) in 1992. KBOs are found outward from the orbit of Neptune to ~55 AU. Pluto is within this region and is one of the largest KBOs. Thousands of these objects are now known to exist, including Eris, which is thought to be slightly larger than Pluto, and Quaoar, Makemake, Haumea, and Ixion, all of which are at least half as large as Pluto. Pluto is not alone in the outer Solar System, nor is it unique.

Beyond the Kuiper Belt there has been theorized to exist the Oort cloud, filled with additional icy debris left over from the early formation of the solar system. It is from the Oort cloud that comets may originate.

We now know (thanks to increasingly powerful telescopes and spacecraft exploration) that objects in the Solar System come in a remarkable variety of shapes, sizes and compositions. The classical planets are all spheroidal. The inner planets and asteroids are rocky. The outer planets are gaseous or liquid metal. The KBOs are icy (probably mostly methane and water ice). The largest of the asteroids and KBOs are also spheroidal; this an inescable consequence of physics—at some point an object becomes large enough that its self gravity causes it to collapse upon itself and reaches so-called hydrostatic equilibrium. At the very small end of the size distribution, we know there exist small grains of dust. Thus, the Solar System is populated by objects smaller than a dust grain and as large as the Sun with a continuum of objects in between.

Asteroids can occasionally present a hazard to the Earth (just ask the dinosaurs). Recent efforts to survey the asteroid belt for those objects that may pose a future hazard has resulted in a very well characterized size distribution. As the size of asteroids decreases, the number of asteroids increases. In other words, there are just a few very large asteroids (Ceres, Vesta), and thousands upon thousands of the very small (under 100 m).

The size distribution of asteroids surveyed by the Sloan Telescope. The population number is normalized the population of 10 km objects. The asteroid population is a continuum, as is the population of objects in the Solar System. (Image credit: Unknown).

If the origin of the classical planets and their moons, the asteroids, the KBOs, and the uncountable dust grains were different, these different origins might serve as a means by which to establish a scientific categorization. However, the origin of all these objects is the same. All the objects are the result of countless collisions and gravitational collapse of a protoplanetary disk. It is the collision and accretion that results in the nearly log-normal size continuum of objects in the Solar System. Asteroids are just the bits of rubble left over that were not accreted by larger objects. The asteroids themselves may very well be conglomerations of smaller bits of dust and rock rather than the more solid monolithic structures of the science fiction genera. KBOs are the bits of rubble in the Outer Solar System that were not accreted.

So here we are today. We inherited the term planet, originally used to describe the wandering nature of objects against the more predictable background stars. Millennia ago, we were aware of only a handful of these objects. In time we found that the wanderers were not only distinct from stars in their journey across the sky, but that they were not stars at all; they really were in a class by themselves. The idea of planet made sense. Then, we found that there were more than just a handful of planets. First there were dozens, then hundreds, then thousands, then tens of thousands! It still makes sense to distinguish these objects from stars, as they are quite clearly different (for example, there is no nuclear fusion and they are not at the center of the Solar System).

What does not make scientific sense is to further scientifically categorize the range of solar system objects. Doing so inherently requires defining arbitrary defining lines in a size continuum. While such dividing lines can certainly be legislated by such bodies as the International Astronomical Union (IAU), they have no meaningful basis, and such an exercise merely brings to light the hubris of man trying to sort nature into boxes and bins.

In time, the concept of a planet will find its way to the dust bins of astronomical rubbish, atop celestial spheres and the geocentric model of the Solar System. Astronomers of the future will recognize the continuum of objects in our Solar System and in extra solar systems, too. Any distinction between objects will be one of convenience rather than of scientific purpose, just as asteroids were once distinguished from planets solely for convenience. Historians of science will study the transition of the Classical Planetary Model to the Modern Solar System Continuum Model, and children of the future will chuckle at the silly argument made over whether Pluto is a planet, just as we all chuckle over the argument of a circular or rectangular flat Earth.

Wednesday, December 16, 2009

I just returned to my hotel after attending my first day at this year's American Geophysical Union Fall Conference in San Francisco. The meeting started on Monday and runs through the entire week. It is the largest meeting by far for the Earth and Planetary Sciences with well over 12,000 scientists in attendance.

After listening in on this morning's session on Venus, and prior to the Venus poster session, I found myself with a couple of hours of unscheduled time. It didn't make sense to walk back to the hotel, as I would have to turn around an hour later and walk back the Moscone Conference Center. Instead, motivated by some recent discussions on internet fora, I decided to attend a few talks and browse a few poster presentations related to global and regional climate change.
It was a bit like coming home. My education is firmly grounded in the Earth and Atmospheric Sciences. All my graduate research was related to the Earth's atmosphere. It's only in the last decade that I transitioned to planetary work. Not surprisingly, I ran into a few old friends and grad school buddies that remained in the terrestrial scientific community. I was able to catch up on a few topics that I hadn't thought about for quite some time. I even took note of a few terrestrial studies that might have some application to the work I'm currently doing on Mars and Titan.

A picture paints a thousand words, but unfortunately the camera in phone decided to go kaput, so let me describe what I saw at the poster sessions, hopefully in less than a thousand words. Imagine a room the size of a football stadium. Now double it. This is roughly the size of the room allocated to display posters. Within this room are dozens of aisles of bulletin boards, numbered from one to approximately 2,000. Each day, the posters change, resulting in the display of roughly 10,000 scientific presentations over the conference period. [Edit: Turns out there are gaps in the numbering, so that actual number of posters is actually close to several thousand.] The aisles of posters are categorized into broad topics like "Planetary Science", "Atmospheric Science", "Seismology", etc. Within these broad categories there is further categorization into subfields such as "Climate Change", "Climate Observations", "Regional Modeling", "Stratospheric Dynamics", etc. In order to avoid mass congestion, poster presentations are scheduled on a staggered system; only about one-half of the room has active presentations at any given time, although all the posters are up for perusal. The scientific content in the room is massive.

A good fraction of the posters are related to climate and climate change. Some directly target the issue of anthropogenic global warming (AGW), some are tangentially related to AGW and investigate, for example, global and regional climate model accuracies. Other posters look at various observational records, while still others focus on the intersection of science and policy. Just about every angle on the AGW issue is covered in some manner.

Clearly, given what I've just described, it was not possible to read every poster in detail. Likewise, there are so many lectures on climate science, that they are often scheduled on top of one another; it's not possible to attend every talk. Still, most posters have a summary section or conclusion section that can be read in just a couple of minutes. Based on the talks I did attend, on reading some posters in detail, on reading most of the poster conclusions, and on talking with a variety of the presenters, there is only one possible conclusion that can be reached regarding the consensus of experts on AGW:

There is overwhelming scientific consensus on the issue of Anthropogenic Global Warming. That consensus is that humans are producing a warming of the climate due to the emission of CO2 and the positive climate feedbacks that result from that emission.

To deny this overwhelming consensus is to deny gravitation, the heliocentric model of the solar system, or the spheroidal nature of the Earth. Let me make it perfectly clear, however, that this is no way means that the consensus is correct. Neither is this consensus unanimous. There were clearly speakers and poster presentations that were contrary to the consensus, but they were in the minority by far. Really far.

I don't expect that the random qualitative sampling I did today would be much different than any other days, but I'll pop in on the climate presentations over the next few days just to confirm. If anything changes, I'll post an update.

The next time you hear someone forward the argument about a lack of consensus on AGW, tell them to go to the AGU meeting and collect some data. There is only one conclusion that can be reached after such an exercise. The conclusion is inescapable and irrefutable. The overwhelming consensus is that AGW is here. There may be other arguments against AGW, but the "lack of consensus" argument is dead on arrival.